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26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4BetheHeitler5DModel.cc
33 //
34 // Authors:
35 // Igor Semeniouk and Denis Bernard,
36 // LLR, Ecole polytechnique & CNRS/IN2P3, 91128 Palaiseau, France
37 //
38 // Acknowledgement of the support of the French National Research Agency
39 // (ANR-13-BS05-0002).
40 //
41 // Reference: Nucl. Instrum. Meth. A 899 (2018) 85 (arXiv:1802.08253 [hep-ph])
42 // Nucl. Instrum. Meth., A 936 (2019) 290
43 //
44 // Class Description:
45 //
46 // Generates the conversion of a high-energy photon to an e+e- pair, either in the field of an
47 // atomic electron (triplet) or nucleus (nuclear).
48 // Samples the five-dimensional (5D) differential cross-section analytical expression:
49 // . Non polarized conversion:
50 // H.A. Bethe, W. Heitler, Proc. R. Soc. Lond. Ser. A 146 (1934) 83.
51 // . Polarized conversion:
52 // T. H. Berlin and L. Madansky, Phys. Rev. 78 (1950) 623,
53 // M. M. May, Phys. Rev. 84 (1951) 265,
54 // J. M. Jauch and F. Rohrlich, The theory of photons and electrons, 1976.
55 //
56 // All the above expressions are named "Bethe-Heitler" here.
57 //
58 // Bethe & Heitler, put in Feynman diagram parlance, compute only the two dominant diagrams of
59 // the first order Born development, which is an excellent approximation for nuclear conversion
60 // and for high-energy triplet conversion.
61 //
62 // Only the linear polarisation of the incoming photon takes part in these expressions.
63 // The circular polarisation of the incoming photon does not (take part) and no polarisation
64 // is transfered to the final leptons.
65 //
66 // In case conversion takes place in the field of an isolated nucleus or electron, the bare
67 // Bethe-Heitler expression is used.
68 //
69 // In case the nucleus or the electron are part of an atom, the screening of the target field
70 // by the other electrons of the atom is described by a simple form factor, function of q2:
71 // . nuclear: N.F. Mott, H.S.W. Massey, The Theory of Atomic Collisions, 1934.
72 // . triplet: J.A. Wheeler and W.E. Lamb, Phys. Rev. 55 (1939) 858.
73 //
74 // The nuclear form factor that affects the probability of very large-q2 events, is not considered.
75 //
76 // In principle the code is valid from threshold, that is from 2 * m_e c^2 for nuclear and from
77 // 4 * m_e c^2 for triplet, up to infinity, while in pratice the divergence of the differential
78 // cross section at small q2 and, at high-energy, at small polar angle, make it break down at
79 // some point that depends on machine precision.
80 //
81 // Very-high-energy (above a few tens of TeV) LPM suppression effects in the normalized differential
82 // cross-section are not considered.
83 //
84 // The 5D differential cross section is sampled without any high-energy nor small
85 // angle approximation(s).
86 // The generation is strictly energy-momentum conserving when all particles in the final state
87 // are taken into account, that is, including the recoiling target.
88 // (In contrast with the BH expressions taken at face values, for which the electron energy is
89 // taken to be EMinus = GammaEnergy - EPlus)
90 //
91 // Tests include the examination of 1D distributions: see TestEm15
92 //
93 // Total cross sections are not computed (we inherit from other classes).
94 // We just convert a photon on a target when asked to do so.
95 //
96 // Pure nuclear, pure triplet and 1/Z triplet/nuclear mixture can be generated.
97 //
98 // -------------------------------------------------------------------
99
100 #include "G4BetheHeitler5DModel.hh"
101 #include "G4EmParameters.hh"
102
103 #include "G4PhysicalConstants.hh"
104 #include "G4SystemOfUnits.hh"
105 #include "G4Electron.hh"
106 #include "G4Positron.hh"
107 #include "G4Gamma.hh"
108 #include "G4IonTable.hh"
109 #include "G4NucleiProperties.hh"
110
111 #include "Randomize.hh"
112 #include "G4ParticleChangeForGamma.hh"
113 #include "G4Pow.hh"
114 #include "G4Log.hh"
115 #include "G4Exp.hh"
116
117 #include "G4LorentzVector.hh"
118 #include "G4ThreeVector.hh"
119 #include "G4RotationMatrix.hh"
120
121 #include <cassert>
122
123 const G4int kEPair = 0;
124 const G4int kMuPair = 1;
125
126
127 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
128
129 G4BetheHeitler5DModel::G4BetheHeitler5DModel(const G4ParticleDefinition* pd,
130 const G4String& nam)
131 : G4PairProductionRelModel(pd, nam),
132 fLepton1(G4Electron::Definition()),fLepton2(G4Positron::Definition()),
133 fTheMuPlus(nullptr),fTheMuMinus(nullptr),
134 fVerbose(1),
135 fConversionType(0),
136 fConvMode(kEPair),
137 iraw(false)
138 {
139 theIonTable = G4IonTable::GetIonTable();
140 //Q: Do we need this on Model
141 SetLowEnergyLimit(2*fTheElectron->GetPDGMass());
142 }
143
144 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
145
146 G4BetheHeitler5DModel::~G4BetheHeitler5DModel() = default;
147
148 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
149
150 void G4BetheHeitler5DModel::Initialise(const G4ParticleDefinition* part,
151 const G4DataVector& vec)
152 {
153 G4PairProductionRelModel::Initialise(part, vec);
154
155 G4EmParameters* theManager = G4EmParameters::Instance();
156 // place to initialise model parameters
157 // Verbosity levels: ( Can redefine as needed, but some consideration )
158 // 0 = nothing
159 // > 2 print results
160 // > 3 print rejection warning from transformation (fix bug from gammaray .. )
161 // > 4 print photon direction & polarisation
162 fVerbose = theManager->Verbose();
163 fConversionType = theManager->GetConversionType();
164 //////////////////////////////////////////////////////////////
165 // iraw :
166 // true : isolated electron or nucleus.
167 // false : inside atom -> screening form factor
168 iraw = theManager->OnIsolated();
169 // G4cout << "BH5DModel::Initialise verbose " << fVerbose
170 // << " isolated " << iraw << " ctype "<< fConversionType << G4endl;
171
172 //Q: Do we need this on Model
173 // The Leptons defined via SetLeptonPair(..) method
174 SetLowEnergyLimit(2*CLHEP::electron_mass_c2);
175 }
176
177 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
178
179 void G4BetheHeitler5DModel::SetLeptonPair(const G4ParticleDefinition* p1,
180 const G4ParticleDefinition* p2)
181 {
182 G4int pdg1 = p1->GetPDGEncoding();
183 G4int pdg2 = p2->GetPDGEncoding();
184 G4int pdg = std::abs(pdg1);
185 if ( pdg1 != -pdg2 || (pdg != 11 && pdg != 13) ) {
186 G4ExceptionDescription ed;
187 ed << " Wrong pair of leptons: " << p1->GetParticleName()
188 << " and " << p1->GetParticleName();
189 G4Exception("G4BetheHeitler5DModel::SetLeptonPair","em0007",
190 FatalErrorInArgument, ed, "");
191 } else {
192 if ( pdg == 11 ) {
193 SetConversionMode(kEPair);
194 if( pdg1 == 11 ) {
195 fLepton1 = p1;
196 fLepton2 = p2;
197 } else {
198 fLepton1 = p2;
199 fLepton2 = p1;
200 }
201 if (fVerbose > 0)
202 G4cout << "G4BetheHeitler5DModel::SetLeptonPair conversion to e+ e-"
203 << G4endl;
204 } else {
205 SetConversionMode(kMuPair);
206 if( pdg1 == 13 ) {
207 fLepton1 = p1;
208 fLepton2 = p2;
209 } else {
210 fLepton1 = p2;
211 fLepton2 = p1;
212 }
213 fTheMuPlus = fLepton2;
214 fTheMuMinus= fLepton1;
215 if (fVerbose > 0)
216 G4cout << "G4BetheHeitler5DModel::SetLeptonPair conversion to mu+ mu-"
217 << G4endl;
218 }
219 }
220 }
221
222 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
223
224 G4double G4BetheHeitler5DModel::MaxDiffCrossSection(const G4double* par,
225 G4double Z,
226 G4double e,
227 G4double loge) const
228 {
229 const G4double Q = e/par[9];
230 return par[0] * G4Exp((par[2]+loge*par[4])*loge)
231 / (par[1]+ G4Exp(par[3]*loge)+G4Exp(par[5]*loge))
232 * (1+par[7]*G4Exp(par[8]*G4Log(Z))*Q/(1+Q));
233 }
234
235 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
236
237 void
238 G4BetheHeitler5DModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
239 const G4MaterialCutsCouple* couple,
240 const G4DynamicParticle* aDynamicGamma,
241 G4double, G4double)
242 {
243 // MeV
244 static const G4double ElectronMass = CLHEP::electron_mass_c2;
245
246 const G4double LeptonMass = fLepton1->GetPDGMass();
247 const G4double LeptonMass2 = LeptonMass*LeptonMass;
248
249 static const G4double alpha0 = CLHEP::fine_structure_const;
250 // mm
251 static const G4double r0 = CLHEP::classic_electr_radius;
252 // mbarn
253 static const G4double r02 = r0*r0*1.e+25;
254 static const G4double twoPi = CLHEP::twopi;
255 static const G4double factor = alpha0 * r02 / (twoPi*twoPi);
256 // static const G4double factor1 = pow((6.0 * pi),(1.0/3.0))/(8.*alpha0*ElectronMass);
257 static const G4double factor1 = 2.66134007899/(8.*alpha0*ElectronMass);
258 //
259 G4double PairInvMassMin = 2.*LeptonMass;
260 G4double TrThreshold = 2.0 * ( (LeptonMass2)/ElectronMass + LeptonMass);
261
262 //
263 static const G4double nu[2][10] = {
264 //electron
265 { 0.0227436, 0.0582046, 3.0322675, 2.8275065, -0.0034004,
266 1.1212766, 1.8989468, 68.3492750, 0.0211186, 14.4},
267 //muon
268 {0.67810E-06, 0.86037E+05, 2.0008395, 1.6739719, -0.0057279,
269 1.4222, 0.0, 263230.0, 0.0521, 51.1338}
270 };
271 static const G4double tr[2][10] = {
272 //electron
273 { 0.0332350, 4.3942537, 2.8515925, 2.6351695, -0.0031510,
274 1.5737305, 1.8104647, 20.6434021, -0.0272586, 28.9},
275 //muon
276 {0.10382E-03, 0.14408E+17, 4.1368679, 3.2662121, -0.0163091,
277 0.0000, 0.0, 0.0, 0.0000, 1.0000}
278 };
279 //
280 static const G4double para[2][3][2] = {
281 //electron
282 { {11., -16.},{-1.17, -2.95},{-2., -0.5} },
283 //muon
284 { {17.5, 1.},{-1.17, -2.95},{2., 6.} }
285 };
286 //
287 static const G4double correctionIndex = 1.4;
288 //
289 const G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
290 // Protection, Will not be true tot cross section = 0
291 if ( GammaEnergy <= PairInvMassMin) { return; }
292
293 const G4double GammaEnergy2 = GammaEnergy*GammaEnergy;
294
295 //////////////////////////////////////////////////////////////
296 const G4ParticleMomentum GammaDirection =
297 aDynamicGamma->GetMomentumDirection();
298 G4ThreeVector GammaPolarization = aDynamicGamma->GetPolarization();
299
300 // The protection polarization perpendicular to the direction vector,
301 // as it done in G4LivermorePolarizedGammaConversionModel,
302 // assuming Direction is unitary vector
303 // (projection to plane) p_proj = p - (p o d)/(d o d) x d
304 if ( GammaPolarization.howOrthogonal(GammaDirection) != 0) {
305 GammaPolarization -= GammaPolarization.dot(GammaDirection) * GammaDirection;
306 }
307 // End of Protection
308 //
309 const G4double GammaPolarizationMag = GammaPolarization.mag();
310
311 //////////////////////////////////////////////////////////////
312 // target element
313 // select randomly one element constituting the material
314 const G4Element* anElement = SelectTargetAtom(couple, fTheGamma, GammaEnergy,
315 aDynamicGamma->GetLogKineticEnergy() );
316 // Atomic number
317 const G4int Z = anElement->GetZasInt();
318 const G4int A = SelectIsotopeNumber(anElement);
319 const G4double iZ13 = 1./anElement->GetIonisation()->GetZ3();
320 const G4double targetMass = G4NucleiProperties::GetNuclearMass(A, Z);
321
322 const G4double NuThreshold = 2.0 * ( (LeptonMass2)/targetMass + LeptonMass);
323 // No conversion possible below nuclear threshold
324 if ( GammaEnergy <= NuThreshold) { return; }
325
326 CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
327
328 // itriplet : true -- triplet, false -- nuclear.
329 G4bool itriplet = false;
330 if (fConversionType == 1) {
331 itriplet = false;
332 } else if (fConversionType == 2) {
333 itriplet = true;
334 if ( GammaEnergy <= TrThreshold ) return;
335 } else if ( GammaEnergy > TrThreshold ) {
336 // choose triplet or nuclear from a triplet/nuclear=1/Z
337 // total cross section ratio.
338 // approximate at low energies !
339 if(rndmEngine->flat()*(Z+1) < 1.) {
340 itriplet = true;
341 }
342 }
343
344 //
345 const G4double RecoilMass = itriplet ? ElectronMass : targetMass;
346 const G4double RecoilMass2 = RecoilMass*RecoilMass;
347 const G4double sCMS = 2.*RecoilMass*GammaEnergy + RecoilMass2;
348 const G4double sCMSPlusRM2 = sCMS + RecoilMass2;
349 const G4double sqrts = std::sqrt(sCMS);
350 const G4double isqrts2 = 1./(2.*sqrts);
351 //
352 const G4double PairInvMassMax = sqrts-RecoilMass;
353 const G4double PairInvMassRange = PairInvMassMax/PairInvMassMin;
354 const G4double lnPairInvMassRange = G4Log(PairInvMassRange);
355
356 // initial state. Defines z axis of "0" frame as along photon propagation.
357 // Since CMS(0., 0., GammaEnergy, GammaEnergy+RecoilMass) set some constants
358 const G4double betaCMS = G4LorentzVector(0.0,0.0,GammaEnergy,GammaEnergy+RecoilMass).beta();
359
360 // maximum value of pdf
361 const G4double EffectiveZ = iraw ? 0.5 : Z;
362 const G4double Threshold = itriplet ? TrThreshold : NuThreshold;
363 const G4double AvailableEnergy = GammaEnergy - Threshold;
364 const G4double LogAvailableEnergy = G4Log(AvailableEnergy);
365 //
366 const G4double MaxDiffCross = itriplet
367 ? MaxDiffCrossSection(tr[fConvMode],
368 EffectiveZ, AvailableEnergy, LogAvailableEnergy)
369 : MaxDiffCrossSection(nu[fConvMode],
370 EffectiveZ, AvailableEnergy, LogAvailableEnergy);
371 //
372 // 50% safety marging factor
373 const G4double ymax = 1.5 * MaxDiffCross;
374 // x1 bounds
375 const G4double xu1 = (LogAvailableEnergy > para[fConvMode][2][0])
376 ? para[fConvMode][0][0] +
377 para[fConvMode][1][0]*LogAvailableEnergy
378 : para[fConvMode][0][0] +
379 para[fConvMode][2][0]*para[fConvMode][1][0];
380 const G4double xl1 = (LogAvailableEnergy > para[fConvMode][2][1])
381 ? para[fConvMode][0][1] +
382 para[fConvMode][1][1]*LogAvailableEnergy
383 : para[fConvMode][0][1] +
384 para[fConvMode][2][1]*para[fConvMode][1][1];
385 //
386 G4LorentzVector Recoil;
387 G4LorentzVector LeptonPlus;
388 G4LorentzVector LeptonMinus;
389 G4double pdf = 0.;
390
391 G4double rndmv6[6] = {0.0};
392 const G4double corrFac = 1.0/(correctionIndex + 1.0);
393 const G4double expLowLim = -20.;
394 const G4double logLowLim = G4Exp(expLowLim/corrFac);
395 G4double z0, z1, z2, x0, x1;
396 G4double betheheitler, sinTheta, cosTheta, dum0;
397 // START Sampling
398 do {
399
400 rndmEngine->flatArray(6, rndmv6);
401
402 //////////////////////////////////////////////////
403 // pdf pow(x,c) with c = 1.4
404 // integral y = pow(x,(c+1))/(c+1) @ x = 1 => y = 1 /(1+c)
405 // invCdf exp( log(y /* *( c + 1.0 )/ (c + 1.0 ) */ ) /( c + 1.0) )
406 //////////////////////////////////////////////////
407
408 z0 = (rndmv6[0] > logLowLim) ? G4Log(rndmv6[0])*corrFac : expLowLim;
409 G4double X1 = (z0 > expLowLim) ? G4Exp(z0) : 0.0;
410 z1 = xl1 + (xu1 - xl1)*rndmv6[1];
411 if (z1 > expLowLim) {
412 x0 = G4Exp(z1);
413 dum0 = 1.0/(1.0 + x0);
414 x1 = dum0*x0;
415 cosTheta = -1.0 + 2.0*x1;
416 sinTheta = 2*std::sqrt(x1*(1.0 - x1));
417 } else {
418 x0 = 0.0;
419 dum0 = 1.0;
420 cosTheta = -1.0;
421 sinTheta = 0.0;
422 }
423
424 z2 = X1*X1*lnPairInvMassRange;
425 const G4double PairInvMass = PairInvMassMin*((z2 > 1.e-3) ? G4Exp(z2) : 1 + z2 + 0.5*z2*z2);
426
427 // cos and sin theta-lepton
428 const G4double cosThetaLept = std::cos(pi*rndmv6[2]);
429 // sin(ThetaLept) is always in [0,+1] if ThetaLept is in [0,pi]
430 const G4double sinThetaLept = std::sqrt((1.-cosThetaLept)*(1.+cosThetaLept));
431 // cos and sin phi-lepton
432 const G4double cosPhiLept = std::cos(twoPi*rndmv6[3]-pi);
433 // sin(PhiLept) is in [-1,0] if PhiLept in [-pi,0) and
434 // is in [0,+1] if PhiLept in [0,+pi]
435 const G4double sinPhiLept = std::copysign(std::sqrt((1.-cosPhiLept)*(1.+cosPhiLept)),rndmv6[3]-0.5);
436 // cos and sin phi
437 const G4double cosPhi = std::cos(twoPi*rndmv6[4]-pi);
438 const G4double sinPhi = std::copysign(std::sqrt((1.-cosPhi)*(1.+cosPhi)),rndmv6[4]-0.5);
439
440 //////////////////////////////////////////////////
441 // frames:
442 // 3 : the laboratory Lorentz frame, Geant4 axes definition
443 // 0 : the laboratory Lorentz frame, axes along photon direction and polarisation
444 // 1 : the center-of-mass Lorentz frame
445 // 2 : the pair Lorentz frame
446 //////////////////////////////////////////////////
447
448 // in the center-of-mass frame
449
450 const G4double RecEnergyCMS = (sCMSPlusRM2-PairInvMass*PairInvMass)*isqrts2;
451 const G4double LeptonEnergy2 = PairInvMass*0.5;
452
453 // New way of calucaltion thePRecoil to avoid underflow
454 G4double abp = std::max((2.0*GammaEnergy*RecoilMass -
455 PairInvMass*PairInvMass + 2.0*PairInvMass*RecoilMass)*
456 (2.0*GammaEnergy*RecoilMass -
457 PairInvMass*PairInvMass - 2.0*PairInvMass*RecoilMass),0.0);
458
459 G4double thePRecoil = std::sqrt(abp) * isqrts2;
460
461 // back to the center-of-mass frame
462 Recoil.set( thePRecoil*sinTheta*cosPhi,
463 thePRecoil*sinTheta*sinPhi,
464 thePRecoil*cosTheta,
465 RecEnergyCMS);
466
467 // in the pair frame
468 const G4double thePLepton = std::sqrt( (LeptonEnergy2-LeptonMass)
469 *(LeptonEnergy2+LeptonMass));
470
471 LeptonPlus.set(thePLepton*sinThetaLept*cosPhiLept,
472 thePLepton*sinThetaLept*sinPhiLept,
473 thePLepton*cosThetaLept,
474 LeptonEnergy2);
475
476 LeptonMinus.set(-LeptonPlus.x(),
477 -LeptonPlus.y(),
478 -LeptonPlus.z(),
479 LeptonEnergy2);
480
481
482 // Normalisation of final state phase space:
483 // Section 47 of Particle Data Group, Chin. Phys. C, 40, 100001 (2016)
484 // const G4double Norme = Recoil1.vect().mag() * LeptonPlus2.vect().mag();
485 const G4double Norme = Recoil.vect().mag() * LeptonPlus.vect().mag();
486
487 // e+, e- to CMS frame from pair frame
488
489 // boost vector from Pair to CMS
490 const G4ThreeVector pair2cms =
491 G4LorentzVector( -Recoil.x(), -Recoil.y(), -Recoil.z(),
492 sqrts-RecEnergyCMS).boostVector();
493
494 LeptonPlus.boost(pair2cms);
495 LeptonMinus.boost(pair2cms);
496
497 // back to the laboratory frame (make use of the CMS(0,0,Eg,Eg+RM)) form
498
499 Recoil.boostZ(betaCMS);
500 LeptonPlus.boostZ(betaCMS);
501 LeptonMinus.boostZ(betaCMS);
502
503 // Jacobian factors
504 const G4double Jacob0 = x0*dum0*dum0;
505 const G4double Jacob1 = 2.*X1*lnPairInvMassRange*PairInvMass;
506 const G4double Jacob2 = std::abs(sinThetaLept);
507
508 // there is no probability to have a lepton with zero momentum
509 // X and Y components of momentum may be zero, in that case SinPhi=1, cosPhi=0
510 const G4double EPlus = LeptonPlus.t();
511 const G4double PPlus = LeptonPlus.vect().mag();
512 const G4double pPX = LeptonPlus.x();
513 const G4double pPY = LeptonPlus.y();
514 const G4double pPZ = LeptonPlus.z();
515 G4double sinPhiPlus = 1.0;
516 G4double cosPhiPlus = 0.0;
517 G4double sinThetaPlus = 0.0;
518 G4double cosThetaPlus = pPZ/PPlus;
519 if (cosThetaPlus < 1.0 && cosThetaPlus > -1.0) {
520 sinThetaPlus = std::sqrt((1.0 - cosThetaPlus)*(1.0 + cosThetaPlus));
521 sinPhiPlus = pPY/(PPlus*sinThetaPlus);
522 cosPhiPlus = pPX/(PPlus*sinThetaPlus);
523 }
524
525 // denominators:
526 // the two cancelling leading terms for forward emission at high energy, removed
527 const G4double elMassCTP = LeptonMass*cosThetaPlus;
528 const G4double ePlusSTP = EPlus*sinThetaPlus;
529 const G4double DPlus = (elMassCTP*elMassCTP + ePlusSTP*ePlusSTP)
530 /(EPlus + PPlus*cosThetaPlus);
531
532 // there is no probability to have a lepton with zero momentum
533 // X and Y components of momentum may be zero, in that case SinPhi=0, cosPhi=1
534 const G4double EMinus = LeptonMinus.t();
535 const G4double PMinus = LeptonMinus.vect().mag();
536 const G4double ePX = LeptonMinus.x();
537 const G4double ePY = LeptonMinus.y();
538 const G4double ePZ = LeptonMinus.z();
539 G4double sinPhiMinus = 0.0;
540 G4double cosPhiMinus = 1.0;
541 G4double sinThetaMinus = 0.0;
542 G4double cosThetaMinus = ePZ/PMinus;
543 if (cosThetaMinus < 1.0 && cosThetaMinus > -1.0) {
544 sinThetaMinus = std::sqrt((1.0 - cosThetaMinus)*(1.0 + cosThetaMinus));
545 sinPhiMinus = ePY/(PMinus*sinThetaMinus);
546 cosPhiMinus = ePX/(PMinus*sinThetaMinus);
547 }
548
549 const G4double elMassCTM = LeptonMass*cosThetaMinus;
550 const G4double eMinSTM = EMinus*sinThetaMinus;
551 const G4double DMinus = (elMassCTM*elMassCTM + eMinSTM*eMinSTM)
552 /(EMinus + PMinus*cosThetaMinus);
553
554 // cos(phiMinus-PhiPlus)
555 const G4double cosdPhi = cosPhiPlus*cosPhiMinus + sinPhiPlus*sinPhiMinus;
556 const G4double PRec = Recoil.vect().mag();
557 const G4double q2 = PRec*PRec;
558
559 const G4double BigPhi = -LeptonMass2 / (GammaEnergy*GammaEnergy2 * q2*q2);
560
561 G4double FormFactor = 1.;
562 if (!iraw) {
563 if (itriplet) {
564 const G4double qun = factor1*iZ13*iZ13;
565 const G4double nun = qun * PRec;
566 if (nun < 1.) {
567 FormFactor = (nun < 0.01) ? (13.8-55.4*std::sqrt(nun))*nun
568 : std::sqrt(1-(nun-1)*(nun-1));
569 } // else FormFactor = 1 by default
570 } else {
571 const G4double dum3 = 217.*PRec*iZ13;
572 const G4double AFF = 1./(1. + dum3*dum3);
573 FormFactor = (1.-AFF)*(1-AFF);
574 }
575 } // else FormFactor = 1 by default
576
577 if (GammaPolarizationMag==0.) {
578 const G4double pPlusSTP = PPlus*sinThetaPlus;
579 const G4double pMinusSTM = PMinus*sinThetaMinus;
580 const G4double pPlusSTPperDP = pPlusSTP/DPlus;
581 const G4double pMinusSTMperDM = pMinusSTM/DMinus;
582 const G4double dunpol = BigPhi*(
583 pPlusSTPperDP *pPlusSTPperDP *(4.*EMinus*EMinus-q2)
584 + pMinusSTMperDM*pMinusSTMperDM*(4.*EPlus*EPlus - q2)
585 + 2.*pPlusSTPperDP*pMinusSTMperDM*cosdPhi
586 *(4.*EPlus*EMinus + q2 - 2.*GammaEnergy2)
587 - 2.*GammaEnergy2*(pPlusSTP*pPlusSTP+pMinusSTM*pMinusSTM)/(DMinus*DPlus));
588 betheheitler = dunpol * factor;
589 } else {
590 const G4double pPlusSTP = PPlus*sinThetaPlus;
591 const G4double pMinusSTM = PMinus*sinThetaMinus;
592 const G4double pPlusSTPCPPperDP = pPlusSTP*cosPhiPlus/DPlus;
593 const G4double pMinusSTMCPMperDM = pMinusSTM*cosPhiMinus/DMinus;
594 const G4double caa = 2.*(EPlus*pMinusSTMCPMperDM+EMinus*pPlusSTPCPPperDP);
595 const G4double cbb = pMinusSTMCPMperDM-pPlusSTPCPPperDP;
596 const G4double ccc = (pPlusSTP*pPlusSTP + pMinusSTM*pMinusSTM
597 +2.*pPlusSTP*pMinusSTM*cosdPhi)/ (DMinus*DPlus);
598 const G4double dtot= 2.*BigPhi*( caa*caa - q2*cbb*cbb - GammaEnergy2*ccc);
599 betheheitler = dtot * factor;
600 }
601 //
602 const G4double cross = Norme * Jacob0 * Jacob1 * Jacob2 * betheheitler
603 * FormFactor * RecoilMass / sqrts;
604 pdf = cross * (xu1 - xl1) / G4Exp(correctionIndex*G4Log(X1)); // cond1;
605 } while ( pdf < ymax * rndmv6[5] );
606 // END of Sampling
607
608 if ( fVerbose > 2 ) {
609 G4double recul = std::sqrt(Recoil.x()*Recoil.x()+Recoil.y()*Recoil.y()
610 +Recoil.z()*Recoil.z());
611 G4cout << "BetheHeitler5DModel GammaEnergy= " << GammaEnergy
612 << " PDF= " << pdf << " ymax= " << ymax
613 << " recul= " << recul << G4endl;
614 }
615
616 // back to Geant4 system
617
618 if ( fVerbose > 4 ) {
619 G4cout << "BetheHeitler5DModel GammaDirection " << GammaDirection << G4endl;
620 G4cout << "BetheHeitler5DModel GammaPolarization " << GammaPolarization << G4endl;
621 G4cout << "BetheHeitler5DModel GammaEnergy " << GammaEnergy << G4endl;
622 G4cout << "BetheHeitler5DModel Conv "
623 << (itriplet ? "triplet" : "nucl") << G4endl;
624 }
625
626 if (GammaPolarizationMag == 0.0) {
627 // set polarization axis orthohonal to direction
628 GammaPolarization = GammaDirection.orthogonal().unit();
629 } else {
630 // GammaPolarization not a unit vector
631 GammaPolarization /= GammaPolarizationMag;
632 }
633
634 // The unit norm vector that is orthogonal to the two others
635 G4ThreeVector yGrec = GammaDirection.cross(GammaPolarization);
636
637 // rotation from gamma ref. sys. to World
638 G4RotationMatrix GtoW(GammaPolarization,yGrec,GammaDirection);
639
640 Recoil.transform(GtoW);
641 LeptonPlus.transform(GtoW);
642 LeptonMinus.transform(GtoW);
643
644 if ( fVerbose > 2 ) {
645 G4cout << "BetheHeitler5DModel Recoil " << Recoil.x() << " " << Recoil.y() << " " << Recoil.z()
646 << " " << Recoil.t() << " " << G4endl;
647 G4cout << "BetheHeitler5DModel LeptonPlus " << LeptonPlus.x() << " " << LeptonPlus.y() << " "
648 << LeptonPlus.z() << " " << LeptonPlus.t() << " " << G4endl;
649 G4cout << "BetheHeitler5DModel LeptonMinus " << LeptonMinus.x() << " " << LeptonMinus.y() << " "
650 << LeptonMinus.z() << " " << LeptonMinus.t() << " " << G4endl;
651 }
652
653 // Create secondaries
654 auto aParticle1 = new G4DynamicParticle(fLepton1,LeptonMinus);
655 auto aParticle2 = new G4DynamicParticle(fLepton2,LeptonPlus);
656
657 // create G4DynamicParticle object for the particle3 ( recoil )
658 G4ParticleDefinition* RecoilPart;
659 if (itriplet) {
660 // triplet
661 RecoilPart = fTheElectron;
662 } else{
663 RecoilPart = theIonTable->GetIon(Z, A, 0);
664 }
665 auto aParticle3 = new G4DynamicParticle(RecoilPart,Recoil);
666
667 // Fill output vector
668 fvect->push_back(aParticle1);
669 fvect->push_back(aParticle2);
670 fvect->push_back(aParticle3);
671
672 // kill incident photon
673 fParticleChange->SetProposedKineticEnergy(0.);
674 fParticleChange->ProposeTrackStatus(fStopAndKill);
675 }
676
677 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
678